The Physical Unit (PU) is a node in the SNA architecture and has the tasks of monitoring and managing the node resources (LU) from the connected links and neighboring stations. The PU type characterizes the hardware
in the SNA networkPU 1.0: terminal node with severely limited features for connecting
end devicesPU 2.0: cluster controller with enhanced features compared to PU
1.0.An example of a PU 2.0 is the control unit
3174PU 2.1: Cluster controller with the functionalities of PU 1 and PU 2.0; additional support of Advanced Peer to Peer Networking (APPN). Networking capability of PU 2.1 among each other. Examples of PU 2.1 are the AS/400 and the RS/6000. PU 2.1 is usually implemented on personal computers (PC) with System Node Control Point
(SNCP) control componentsPUT :Front End Processors (FEP), which act as a control unit to control a network. A PU 4 usually has an SDLC connection to the remote cluster controllers (PU1/PU2) and optional SDLC connections to other PU4 controllers. The polling and addressing of the cluster controllers could be performed directly by the Network Control Program
(NCP). PU5: A host that controls the FEPs and whose resources can be used.